[Challenges and options for advanced training in surgery : An interdisciplinary position paper against the background of the hospital structural reform in Germany]. / Herausforderungen und Chancen für die chirurgische Weiterbildung : Ein fachgesellschaftsübergreifendes Positionspapier vor dem Hintergrund der Krankenhausstrukturreform.

BACKGROUND: Even now the further training in surgery faces considerable challenges. The planned hospital structural reform will result in new bureaucratic and organizational hurdles, which could lead to a considerable loss of quality in advanced surgical training across all disciplines. OBJECTIVE: The aim of this position paper is to describe the current and future challenges for advanced surgical training and to identify possible approaches and opportunities for the further development against the background of the planned hospital structural reform. MATERIAL AND METHODS: For the development of this position paper a committee of representatives of the Young Forums of the German surgical societies identified and critically discussed current problems and challenges of the present residency training system and formulated a list of demands for a sustainable residency training concept. RESULTS: The planned shift to outpatient treatment and centralization were identified as central challenges for surgical residency training. Surgical training must be considered consistently and from the outset in all political reform efforts. In addition to a transparent and cost-appropriate financing of residency training, we call for the involvement of all German surgical societies in the reform process. Furthermore, the social framework conditions for junior surgeons should be considered. CONCLUSION: The structural change in the hospital landscape in Germany, which is being forced by politicians, harbors the risk of a further loss of quality and experience in surgical treatment and training. At the same time, the planned hospital reform offers a unique opportunity to address existing problems and challenges in surgical training and to consider them as a starting point for structural changes which are fit for the future.

Ex vivo evaluation of 3 different right ventricular outflow tract substitutes.

OBJECTIVES: The Ross procedure represents an excellent treatment option in younger patients with aortic stenosis but is limited by poor availability of homografts. In this study, we investigated the hydrodynamic performance of 3 different types of right ventricular outflow tract replacement with pericardium or synthetic material. METHODS: Three different types of valved conduits were constructed using pericardium and/or synthetic material (Group PEPE: pericardial cusps and pericardial conduit, Group PEPR: pericardial cusps and Dacron conduit, Group PRPR: expanded polytetrafluoroethylene cusps and Dacron conduit). The conduits were designed according to the Ozaki method. Their hydrodynamic performance (effective orifice area, mean pressure gradient and leakage volume) were evaluated in a mock circulation loop at different hydrodynamic conditions. RESULTS: Hydrodynamic assessment showed significantly larger effective orifice area of PEPE and PEPR compared to PRPR under all conditions and there were no significant differences between PEPE and PEPR [for condition 2: PEPE 2.43 (2.35-2.54) cm2, PEPR: 2.42 (2.4-2.5) cm2, PRPR: 2.08 (1.97-2.21) cm2, adjusted pairwise comparisons: PEPE versus PEPR: P = 0.80, PEPE versus PRPR: P < 0.001, PEPR versus PRPR: P < 0.001]. Mean pressure gradient was significantly lower for PEPE and PEPR compared with PRPR, whereas no significant differences were seen between PEPE and PEPR. Leakage volume was significantly lower for PEPE and PEPR compared with PRPR under all conditions while leakage was similar between PEPE and PEPR. CONCLUSIONS: Pulmonary graft reconstruction with pericardium cusps showed superior hydrodynamic performance compared with polytetrafluoroethylene cusps. Our results suggest that it could be considered as an alternative substitute for right ventricular outflow tract replacement during the Ross procedure.

Impact of different in vitro models on functional performance of the self-expanding transcatheter heart valve.

OBJECTIVES: Transcatheter heart valves (THVs) are investigated according to International Organization for Standardization requirements using in vitro heart simulators to evaluate hydrodynamic performance. In contrast to surgical valves, a THV's performance heavily depends on the configuration and shape of the aortic anulus. In International Organization for Standardization regulations, there is no detailed definition for the construction of a compartment in which a THV has to be tested. Therefore, the aim of this in vitro study was to compare different in vitro models for functional testing of THVs. METHODS: Porcine aortic conduits (23-mm diameter) were implanted in Dacron prostheses and calcified with double-distilled water and calcification buffer at 37°C over 83 million cycles in a Hi-Cycler (durability testing) mimicking nearly 3 patient-years. Hydrodynamic testing of Evolut PRO 26 mm was performed within 3 models (plexiglass, native conduit and calcified conduit; all 23-mm diameter) at a frequency of 64 bpm and different stroke volumes (55-105 ml). RESULTS: Calcified conduits showed significantly higher mean pressure gradients (MPG) and lower effective orifice areas (EOA) in comparison to native conduits (without THV; P < 0.001). EOA and MPG of Evolut PRO differed depending on the model tested. Calcified conduits resulted in the lowest EOA and highest MPG of the THV compared to plexiglass and the native conduit. Full expansion of the THV was least impaired in the native conduit, while lowest geometric orifice area, lowest minimal internal diameter and highest pin-wheeling index of Evolut PRO were seen in the calcified conduit. CONCLUSIONS: Full expansion and functional performance of the Evolut PRO THV depends on the configuration of the testing compartment in an in vitro setting.

Functional performance of 8 small surgical aortic valve bioprostheses: an in vitro study.

OBJECTIVES: Selection of a surgical aortic valve (SAV) bioprosthesis model for the treatment of aortic valve disease remains controversial. The aim of this study was to characterize the functional performance of 8 SAV models in a standardized in vitro setting. METHODS: The hydrodynamic performance of 8 SAVs with labelled size 21 mm (Avalus™, Hancock® II, Mosaic® Ultra™, Perimount®, Perimount® Magna Ease, Epic™ Supra, Trifecta™ GT; Freestyle®), was investigated in a pulse duplicator. Transvalvular pressure gradients and effective orifice area (EOA) were recorded. The geometrical orifice area and physical dimensions of the valves were determined, and new functional dimensions were introduced. RESULTS: Mean pressure gradient (MPG) and EOA differed significantly between the analysed SAVs. The Epic presented with the lowest EOA and highest MPG, while the Trifecta showed the highest EOA and the lowest MPG. We introduce a useful way to determine the minimal internal diameter and a new measure termed 'relative orifice area' to characterize a valve's performance. CONCLUSIONS: SAVs showed significant differences in their hydrodynamic performance despite the same label size. This finding was related to the construction of the valves. We introduce a new measure that characterizes the functional performance of a valve model and size for the treatment of an aortic annulus of a specific size. Our data emphasize that SAV selection should carefully be done using an individual patient approach and that future research is necessary to improve the current generation of SAVs.

Impact of high-pressure balloon aortic valvuloplasty on the hydrodynamic result after a transcatheter valve-in-valve procedure.

OBJECTIVES: The aim of this study was to investigate the degree of functional improvement of a transcatheter heart valve (THV) for valve-in-valve after bioprosthetic valve fracture (BVF) of three small surgical aortic valve bioprostheses (SAVBP) using high-pressure balloon aortic valvuloplasty (HP-BAV) under standardized ex-vivo-conditions. METHODS: A THV 26 mm (Evolut R) and SAVBP 21 mm (Perimount Magna Ease, Trifecta, and Epic supra [n = 4] were used. Mean pressure gradient (MPG), effective orifice area (EOA), geometric orifice area (GOA), minimal internal diameter (MID), and pinwheeling index (PWI) were analyzed before and after HP-BAV of the SAVBP using a noncompliant balloon. Fracturing of the SAVBP was done before implantation of the THV and the balloon pressures at the point of fracture were recorded. RESULTS: The Magna Ease and Epic fractured at balloon pressures of 18 and 8 atm, respectively. The Trifecta did not fracture up to a balloon pressure of 30 atm but was dilated. HP-BAV led to increased THV expansion as evident by straightened coaptation lines of the Evolut R 26 mm with reduced PWI, increased MID, and increased GOA in all 21 mm SAVBP. Evolut R showed significantly lower MPG and higher EOA as ViV in all prostheses after HP-BAV (p < 0.001). MPG and EOA of Evolut R differed regarding the SAVBP. Evolut R presented the lowest MPG and highest EOA in Magna Ease and the highest MPG and lowest EOA in Epic supra. CONCLUSIONS: The degree of function improvement of the same THV as ViV after HP-BAV depends on the surgical valve model. Functional improvement can also be achieved without valve fracture.

Ex vivo evaluation of the Ozaki procedure in comparison with the native aortic valve and prosthetic valves.

OBJECTIVES: We investigated the hydrodynamic performance and cusp kinematics of the Ozaki neocuspidized aortic valve in comparison with the native aortic and prosthetic valves in an ex vivo study. METHODS: Native aortic valves of swine hearts were replaced by aortic valve substitutes, and their hydrodynamic performance (effective orifice area and mean pressure gradient) was evaluated in a mock circulation under defined conditions. The following aortic valve substitutes were investigated: native aortic valve, Ozaki valve, Perimount Magna Ease, Trifecta and St. Jude Medical Masters. All prosthetic valves had a labelled size of 21 mm. RESULTS: The Ozaki valve and native aortic valve showed a similar and significantly larger orifice area than all investigated prosthetic valves particularly at high flow rates. There was no significant difference between the Ozaki valve and the native aortic valve. The native aortic valve and Ozaki valve showed a similar increase in orifice area with increasing flow through the valve while prosthetic valves showed a markedly weaker increase. Similarly, the native and Ozaki valve showed a similar increase in mPG with forward flow which was weaker than prosthetic valves. Cusp kinematics were similar between the native and Ozaki valve, whilst prosthetic valves were clearly distinguishable from them. CONCLUSIONS: The Ozaki procedure showed excellent hydrodynamic performance compared to prosthetic valves and showed similar cusp motion characteristics to the native aortic valve. Our results suggest that the Ozaki neocuspidized valve behaves physiologically in many aspects, which may contribute to beneficial clinical outcomes.

The figure-of-8 aortic valve suturing technique optimizes the effective orifice area of a small aortic annulus-an ex vivo study.

OBJECTIVES: Surgical aortic valve replacement (SAVR) in small annuli carries an elevated risk for the patient-prosthesis mismatch. In this study, we systematically investigated the influence of different implantation techniques including annular enlargement (AE) on the functional result after SAVR in small annuli using a standardized ex vivo model. METHODS: SAVR using the PERIMOUNT Magna Ease® (PME) 21 mm was performed in small porcine aortic roots using 4 implantation techniques: non-everting pledgeted (NE) suture, single interrupted (SI) suture, continuous suture (CS), figure-of-8 (F8) suture, as well as the PME 23 mm after AE using the Nunez method and the NE suture technique (PME23 AE). The effective orifice area (EOA), mean pressure gradient and leakage volume were evaluated using a mock circulation loop in accordance with ISO regulations. RESULTS: Experiments were conducted on 31 porcine aortic roots. PME21 using F8 and PME23 after AE achieved a significantly larger EOA than using NE. PME23 after AE showed a larger EOA than the PME21 using any suture technique, except the F8 [for stroke volume of 74 ml: PME21 NE: 1.68 (1.63-1.72) cm2, PME21 SI: 1.76 (1.68-1.81) cm2 (P = 0.17), PME21 CS: 1.76 (1.65-1.79) cm2 (P = 0.14), PME21 F8: 1.81 (1.70-1.85) cm2 (P = 0.005); PME23 AE: 1.83 (1.73-1.92) cm2 (P < 0.001)]. SI and CS did not result in larger EOA compared with the NE technique. PME21 using SI had a significantly larger leakage volume than using NE and there was no significant difference between other techniques [for stroke volume of 74 ml: PME21 NE: 3.51 (1.85-4.53) ml/stroke, PME21 SI: 6.00 (4.02-7.06) ml/stroke (P < 0.001), PME21 CS: 4.04 (3.60-4.49) ml/stroke (P = 0.10), PME21 F8: 3.16 (1.99-3.62) ml/stroke (P = 0.74), PME23 NE: 2.89 (2.45-4.72) ml/stroke (P = 0.51)]. CONCLUSIONS: The F8 technique with the PME21 achieved a similar EOA as the 1 size larger PME23 using NE after AE. These results suggest that the F8 technique may be an effective surgical modification to improve the haemodynamic result in a small annulus without additional AE.

Impact of different valve-in-valve positions on the hydrodynamic performance of the newest-generation self-expanding transcatheter heart valve.

OBJECTIVES: Transcatheter aortic valve-in-valve (ViV) procedures are increasingly performed for the treatment of degenerated surgical aortic valves with a high risk for a redo operation. For an optimal functional result, precise positioning of the transcatheter heart valve (THV) inside the SHV is crucial. The aim of this study was to systematically investigate the impact of implantation depth on the functional result after a ViV procedure in a standardized in vitro setting. METHODS: A THV 23 mm (Evolut PRO) and 3 SHV 21 mm (Perimount Magna Ease, Trifecta and Hancock II) were used for hydrodynamic testing with a constant heartbeat 64/min and a range of 55-105 ml of stroke volume in 5 different positions of the THV. The following parameters were analysed: mean pressure gradient (MPG), effective orifice area (EOA), geometric orifice area, minimal internal diameter and pin-wheeling index. RESULTS: MPG and EOA differed significantly regarding the position of the THV in the same SHV. The highest EOA and the lowest MPG were recorded for Evolut PRO with significance for both parameters in Hancock II at 4 vs 5 mm (P < 0.001), in Magna Ease at 2 mm (vs 3 mm and vs 6 mm, P < 0.001) and in Trifecta at 4 mm (vs 5 and 6 mm, P < 0.001). Leaflet coadaptation, minimal internal diameter and maximal geometric orifice area of the same TAV differ regarding the position of the TAV. CONCLUSIONS: The optimal position for hydrodynamic performance of the THV as ViV differs among specific SHV models. The findings may be useful for planning a ViV procedure using the Evolut PRO THV.

Chronic stable heart failure model in ovine species.

Establishing a chronic heart failure (HF) model is challenging, particularly in the ovine model. The aim of this study was to establish a reproducible model of HF in an ovine model. Seventeen sheep were operated using the left thoracotomy approach. Chronic HF was induced through ligation of the diagonal and marginal branches only. Perioperative hemodynamic and echocardiographic parameters were compared. A total of (3 ± 1) coronary ligations were used. Thirteen animals survived the procedure and were followed up for (15 ± 5) days. The mean arterial pressure, heart rate (HR), mean pulmonary artery pressure (mPAP), central venous pressure, and cardiac output at baseline and prior to animal sacrifice was (75 ± 14 mmHg) and (68 ± 16 mmHg) P = .261; (72 ± 9 bpm), (100 ± 28 bpm) P = .01; (15 ± 4 mmHg) and (18 ± 5 mmHg) P = .034; (10 ± 6 mmHg) and (8 ± 4 mmHg) P = .326; (3.4 ± 1 L/min) and (3.9 ± 1 L/min) P = .286, respectively. The LVEF at baseline and prior to animal sacrifice was (63 ± 13%) and (43 ± 6%) P = .012. Twelve surviving animals were supported with LVAD in a follow-up procedure. Chronic stable HF in sheep was successively established. Clinical symptoms and drastic increase in the mPAP and HR as well as echo findings were the most sensitive parameters of HF. This reproducible ovine model has proven to be highly promising for research regarding HF.

Impact of tricuspid valve insufficiency on the performance of left ventricular assist devices.

Objective: To evaluate the impact of severe tricuspid valve insufficiency (TVI) at the time of left ventricular assist device (LVAD) implantation on the hemodynamic and LVAD parameters in an acute ovine model. Methods: Stable heart failure (HF) was induced in 10 ovines through the application of 3 ± 1 coronary ligations. Once stable HF was obtained (after 15 ± 5 days), the animals were supported with an LVAD. Hemodynamic data and pump parameters were obtained and compared in 2 settings; first with LVAD in place after weaning from the cardiopulmonary bypass machine (no TVI condition) and second following the induction of severe TVI through resection of the tricuspid valve (TVI condition). Results: There were no statistically significant differences in the hemodynamic and pump parameters between TVI condition and no TVI conditions except for lower cardiac output in the TVI condition (2 [1.38-2.8] L/min vs 3.2 [1.55-3.7] L/min, P = .027) and the expected greater central venous pressure in the TVI condition (26 [24-31] mm Hg vs 15 [13-25] mm Hg, P = .020). A median pump flow of 2.8 (2.45-3.75) L/min versus 2.9 (2.75-3.8) L/min in the TVI condition and no TVI condition was documented (P = .160). Conclusions: Results from this acute animal study suggest that severe TVI in HF with preserved right ventricular function does not have significant impact on the LVAD pump parameters. The observed reduction in cardiac output may warrant further investigations, especially under loading conditions.

Gastrointestinal Bleeding in Patients with HeartWare Ventricular Assist Device: Does the Activation of the Lavare Cycle Make a Difference?

We aimed to investigate the prevalence of gastrointestinal bleeding (GIB) events in patients supported with HeartWare ventricular assist device (VAD) and activated lavare cycle. Thirty-two GIB events were documented in 22 patients (21%) after median support duration of 22 days (IQR: 11-157 days). There were 13 patients with early episodes of GIB. Meanwhile, 17 GIB events were documented in 9 patients after a median support duration of 174 days (IQR 25-736 days) (late bleeders), accounting for 0.18 events per patient's years. The GIB events appear to be a frequent complication in patients with HeartWare VAD regardless of the lavare cycle.

Prevalence of De Novo Aortic Valve Insufficiency in Patients After HeartWare VAD Implantation with an Intermittent Low-Speed Algorithm.

De novo aortic valve insufficiency (AI) is a frequent occurrence in patients supported with left ventricular assist device (LVAD). The European version of the HeartWare LVAD has intermittent low-speed software (lavare cycle) to facilitate intermittent aortic valve opening. We examined aortic valve opening status and prevalence of AI in patients supported with HeartWare LVAD and activated lavare cycle. HeartWare LVAD patients were prospectively monitored using serial echocardiograms at different time points after the LVAD implantation. Inclusion criteria were patients with no > mild AI and/or no aortic valve surgery at the time of LVAD implantation and at least 60 days of support. Three of 37 patients had aortic valve surgery and were excluded from the analysis. A total of 34 patients with mean age of 57 ± 12 years met the inclusion criteria. After median support duration of 408 days (77-1250 days), eight patients had trace/mild AI (24%) and one patient developed moderate AI (3%). An average pump flow, speed, and mean arterial pressure of 4.4 ± 0.6 L/min, 2,585 ± 147 rpm, and 88 ± 11 mmHg were documented, respectively. Aortic valve opening was persistently seen in 22 patients (65%). Aortic valve opening is frequent, and the development of > mild AI seems to be rare in patients supported with HeartWare LVAD.

Implanting permanent left ventricular assist devices in patients on veno-arterial extracorporeal membrane oxygenation support.

Selected patients who fail to be weaned off temporary veno-arterial extracorporeal membrane oxygenation support may be considered for long-term left ventricular assist devices.  We describe here a left ventricular assist device implantation technique in patients with prior veno-arterial extracorporeal membrane oxygenation support without the use of a cardiopulmonary bypass machine, which minimizes the intraoperative trauma and blood loss while still meeting all the goals of the standard procedure.